The early-life environment can affect the health of offspring, including mental health, later in life. Maternal consumption of diets rich in fat or simple sugars may increase the likelihood of offspring developing anxiety disorders. Some studies on animals have shown this influence. It is common for a variety of apparatuses or mazes to be used to study animal behaviors that are similar to those related to anxiety in humans. These are called anxiety-like behaviors. Animal model studies are important because they can more easily identify the maternal effect and provide ways of studying the underlying mechanisms that could explain the relationship between maternal diet and the development of anxiety in offspring. This chapter presents the findings of studies that have used animal models to investigate anxiety in relation to the period of time during which the mother was exposed to the diet and discusses the underlying mechanisms that may explain these results.